A conventional ultrasonic transducer, for example, a medical mechanical scanning 3D ultrasonic transducer 10 that is transvaginal and transrectal, as shown in FIG. 7, includes a stepper motor 1, which is a driving source of a transducer main body 13, disposed in a housing 11 having a tip with a tapered shape. The conventional ultrasonic transducer includes hubs 4a, 4b, and 4c disposed between an output shaft 1a of the stepper motor 1 and a drive shaft 1c. Then, the hub 4c is screwed to the output shaft 1a of the stepper motor 1 while the hub 4a is screwed to the drive shaft 1c. Metallic disks 2a are each interposed and secured between two of the hubs 4a, 4b, and 4c to transmit torque of the output shaft 1a to the drive shaft 1c, causing the drive shaft 1c to swing by a predetermined angle in normal and reverse directions.
Then, the swing of this drive shaft 1c swings a large bevel gear 7b engaging a small bevel gear 7a on a tip of the drive shaft 1c. This causes normal and reverse swings of the ultrasound transmitting/receiving portion (a piezoelectric element group) 13 about its short-axis direction in ultrasonic propagation medium filled up in a cover 12 fitted into a tip of the housing 11.
When an ultrasonic diagnosis of a patient is performed using the mechanical scanning 3D ultrasonic transducer 10 for medical ultrasonic diagnostic equipment, a surface of the cover 12 of the ultrasonic transducer 10 is inserted into, for example, a vagina and/or a rectum of the patient for contacting their inner wall surfaces or is brought into contact with body surfaces to perform transmission and reception of an ultrasound after a cap 14 is fitted on a lower end portion of the housing 11 shown in FIG. 7 to causes the inside of the housing 11 to be in a sealed state.
Therefore, the mechanical scanning 3D ultrasonic transducer for medical ultrasonic diagnostic equipment, which has a structure that swings the transducer main body 13, is used while its distal end portion contacts the body surface or the inside of a body cavity, such as the vagina and the rectum, of the patient during the ultrasonic diagnosis. Thus, it is necessary that the patient does not feel a vibration, a noise, and/or the like from the transducer main body.